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Thread: Polystyrene Cone shaped hole cutter

  1. #1
    garage nut's Avatar
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    Polystyrene Cone shaped hole cutter

    Got plastic drums for a floating raft hydroponics system. That required a piece of polystyrene floating on the water with holes for the net pots with the plants in them. Usually lettuce.

    So as usual research as to how to make a hot wire cutter. Needed some Nichrome Wire...

    Where to get it...toasters, hair driers, old irons... Wife has a hair drier....Will she notice if I remove one of the heating elements??

    Polystyrene Cone shaped hole cutter-blow-drier-1.jpg

    After careful investigation I removed one element.

    Polystyrene Cone shaped hole cutter-element-removed.jpg

    Perhaps after the cleaning the hair drier will actually work better as it will definitely blow stronger. Filter at the back was totally blocked.

    Wire turned out to be 26 gauge.

    Found a website where you enter gauge, length of wire, temp required and volts and amps are then calculated.

    I needed 2.8V and 6 amps. I recon this is good info if you have a infantile variable power supply. I have a 12v car battery...

    Then to build the little cutter to accommodate the 75mm net pots I drew one out and was going to use a 25mm broomstick as the pivot so extrapolated the angle to determine the length of the broomstick.

    Polystyrene Cone shaped hole cutter-cutter.jpg

    So how it works, I cut 25mm holes in the foam,and then power up the cutter. The broom stick fits nicely in the hole. I then just slowly rotate the broom stick and the angled wire cuts a perfect cone shaped hole in the foam.

    Polystyrene Cone shaped hole cutter-tensioner.jpg

    To keep the tension on the wire once it is warm I fitted 2 elastics on the one end of the wire and pulled then tight in a piece of condute and secured with a steel pin on the other end. I cut the condute at the same angle as the wire to pull in the same direction as the wire.

    To stop the wire burning the broom stick at the bottom I first fitted a 25mm washer, the same at the top a piece of scrap ali plate.

    I fitted 2 wooden washers under the top support. this was in the event that I wanted to cut different sized holes. Then I only have to remove the washers.



    Perhaps this explains it better.

  2. The Following 7 Users Say Thank You to garage nut For This Useful Post:

    bruce.desertrat (12-19-2018), PJs (12-20-2018), Priemsy (12-19-2018), rebuilder1954 (12-19-2018), Seedtick (12-19-2018), that_other_guy (12-20-2018), toma (12-20-2018)

  3. #2

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    Very slick, Garage Nut!

    i did not have a car battery handy for my hot wire cutter, but i had a 120-24v step down transformer. controlled by a dimmer switch, it lets me dial in the right amount of heat for different types and thicknesses of material.

    Bob

  4. The Following 2 Users Say Thank You to rebuilder1954 For This Useful Post:

    PJs (12-20-2018), Priemsy (12-19-2018)

  5. #3
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    Thanks for that idea, I am just always very scared when it comes to wall power I have has some shocking experiences with it already.

    I tried calculating the resistance I would need, but ended up just putting a double contact globe in series. Initially it was too hot and did not give me enough time to change hands while rotating the cutter. Also needed the cutting done quickly so no time to look at adjustable power supply, but your idea is lying in a box somewhere in my garage.

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    PJs (12-20-2018)

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    Thanks garage nut! We've added your Cone Cutter to our Foam Cutters category,
    as well as to your builder page: garage nut's Homemade Tools. Your receipt:





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